1. Field
Certain aspects of the present disclosure generally relate to wireless communications and, more particularly, to methods and apparatuses for supporting television white space (TVWS) communication.
2. Background
Wireless communication networks are widely deployed to provide various communication services such as voice, video, packet data, messaging, broadcast, etc. These wireless networks may be multiple-access networks capable of supporting multiple users by sharing the available network resources. Examples of such multiple-access networks include Code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA) networks, and Single-Carrier FDMA (SC-FDMA) networks.
In order to address the issue of increasing bandwidth requirements demanded for wireless communications systems, different schemes are being developed. One of the schemes, for example, entails expanding Wi-Fi technology to utilize the unused frequency spectrum in the television (TV) band (i.e., the TV white space). The Institute of Electrical and Electronics Engineers (IEEE) 802.11af task group has been formed to define an amendment to the IEEE 802.11 standard for operating in the TV white space (TVWS). The IEEE 802.11 standard denotes a Wireless Local Area Network (WLAN) air interface standard developed by the IEEE 802.11 working group for short-range communications (e.g., tens of meters to a few hundred meters). By using the TVWS with frequencies below 1 GHz, IEEE 802.11af may offer greater propagation distances to be achieved, in addition to the increased bandwidth offered by the unused frequencies in the TV spectrum.
The Federal Communications Commission (FCC) had developed regulations for unlicensed operation in unused TV channels, referred to as TV white space (TVWS). The TV white space devices (WSDs), also referred to by the FCC as TV band devices (TVBDs), may need to meet a number of requirements for operation in the TVWS so as to avoid causing harmful interference to the licensed services in the TV bands (e.g., broadcast TV, wireless microphones, etc).
There are several classes of devices defined by the FCC: fixed and personal/portable devices (referred to as portable devices in this disclosure). There are two classes of portable devices: Mode I and Mode II devices.
The portable Mode II devices may need to have geo-location capability with an accuracy of 50 meters and may need to have Internet access so as to be able to check with a database to find out which channels in its location are white space and available for use. The Mode I devices may not need to have geo-location capability or Internet access, but they can only be permitted to transmit in TV channels which are indicated as available from a Fixed or Mode II device. In addition, the Mode I device after receiving initial enablement from the Fixed or Mode II device may need to receive a “contact verification signal” (CVS) from the Fixed or Mode II device at least every 60 seconds in order to continue the TVWS communication, or the Mode I device may need to cease transmission.
The FCC specifies limits on both the total transmit power, and on the power spectral density (PSD) of the TV white space devices. The maximum transmit power of a portable device can be 20 dBm, and this limit can be lowered to 16 dBm when the portable device is operating on a channel adjacent to a broadcast TV signal. In addition to the power limit, there may be also a PSD limit specified by the FCC, which can be controlled by limiting the maximum power in any 100 kHz band. For portable devices, the limit can be 2.2 dBm in 100 kHz, which can be lowered to −1.8 dBm when operating in a channel adjacent to a TV broadcast signal. The PSD limit can prevent high power narrowband signals.